The objectives of this project are to investigate relationships between differences in personality, sensory thresholds, and autonomic nervous system (ANS) activity in normal humans and to study racial differences in ANS activity. Bilateral skin conductance, heart rate, vasomotor activity, and respiration have been recorded in two sessions in which constant and variable intensity tones and lights are presented, and auditory and two flash thresholds determined by methods which permit signal detection analyses. Several standardized personality tests were also given. The procedures allow determination of the effects of stimulus intensity and heteromodal stimulation on ANS activity. The protocol allows testing of several theoretical models of the relationships of ANS activity, sensory sensitivity, and personality, some of which have implications for the etiology of psychopathology.